1. Technical Field
The present invention relates to a semiconductor light emitting device that includes a semiconductor light emitting element, and in particular to a semiconductor light emitting device that allows light from a light source to efficiently outgo from the semiconductor light emitting device.
2. Description of Related Art
In semiconductor light emitting devices, it has been an important issue to allow light to efficiently outgo from a semiconductor light emitting element as a light source. Accordingly, various types of light emitting devices have been developed. FIG. 25(a) shows a known LED light emitting device 200 (see Japanese Laid-Open Patent Publication No. H07-099345 (1995)). The LED light emitting device 200 is configured to entirely seal a semiconductor light emitting device with a resin member. The semiconductor light emitting member includes a lead frame 202 that includes a cup 203, and an LED 204 that is mounted on the cup 204. Also, the sealing resin member includes a resin material 211 that fills up the interior of the cup 203, and a resin material 212 that entirely encloses the cup 203 including the resin material 211. The resin material 211 that fills up the interior of the cup 203 includes a phosphor material 205 that converts the wavelength of light that is emitted by the LED 204 into a different wavelength, or absorbs a part of the wavelength range light of that is emitted by the LED 204.
Also, FIG. 25(b) is an enlarged schematic cross-sectional view showing a portion of the cup 203 of the LED light emitting device 200 shown in FIG. 25(a). As shown in FIGS. 25(a) and 25(b), the wavelength of emission light from the LED 204 is converted by the resin material 211. Although the converted light is scattered in all directions, most converted light is reflected inside the cup, and is gathered toward the light observation surface side. That is, the light-gathering rate of the converted light is improved.
However, in the thus-configured light emitting device, there is a problem in that a part of light that is reflected inside the cup 203 as return light is incident on the LED 204, and is absorbed by the LED 204. This return light deteriorates the characteristics of the LED 204, and causes reduction of output light and deterioration of the life characteristics of the LED 204.
Also, in order that the LED 204 may be mounted to a mount surface 203a of the cup 203, and that light from the side surface of the LED 204 may be reflected on an inclined surface 203b of the case 203, the area of the mount surface 203a of the case is required to be larger than the bottom surface of the LED 204. In addition to this, the depth of the cup 203 is required to be deep. The reason is to require for the inclined surface 203b of the cup to have a large area in order to reflect emission light from the side surface of the LED 204 inside the cup 203. In addition to this, in order to prevent that light that entering the LED light emitting device 200 from the outside reaches the phosphor material 205, the resin material 211 containing the phosphor material 205 should not bulge out of the cup. For this reason, the cup 203 necessarily has an enough height to surround the side surface of LED 204. Accordingly, the cup 203 is required to be large.
FIG. 26 is a schematic cross-sectional view showing a known laser diode (LD) light emitting device as a semiconductor light emitting device (see FIG. 4 in Japanese Patent Laid-Open Publication No. 2002-270952, and Japanese Laid-Open Patent Publication No. H07-176825 (1995)). In an LD light emitting device 100, an LD 104 is mounted to the side surface of a bar-shaped stem member 102 that is coupled to the upper surface of the stem base 101. The LD 104 is electrically connected to a lead 108 that extends from the lower surface of the stem base 101. Thus, the LD 104 can be connected to an exterior terminal via the lead 108.
The LD light emitting device 100 further includes a cylindrical cap 103 that is arranged on the peripheral portion of the upper surface of the stem base 101. The bar-shaped stem member 102 and the LD 104 are arranged inside the cap 103. The cap 103 has an annular upper surface 103a as the top of the cap 103. An opening 105 is formed in the central part of the upper surface 103a. The opening 105 of the cap penetrates the upper surface 103a of the cap in the vertical direction. The width of the penetrating opening is constant. Also, glass 113 is adhered on the bottom surface of the upper surface 103a of the cap. Thus, the opening 105 of the cap is closed.
In the thus-configured LD light emitting device 100, emission light from the LD 104 passes through the glass 113 and the opening 105 of the cap, and then outgoes from the cap 103. However, there is a problem in that a part of light that travels in the opening 105 of the cap returns toward the LD 104 as return light after being reflected on the wall surface of the opening 105 one time or a plurality of times repeatedly. This may cause reduction of light outgoing efficiency. In addition to this, the return light may cause deterioration of the characteristics of the LD 104.
The present invention is devised to solve the above problems. It is an important object is to provide a semiconductor light emitting device that allows emission light from a semiconductor light emitting element to efficiently outgo from the semiconductor light emitting device so that the light emission intensity of the semiconductor light emitting device is increased.